Fault signaling system for counting chain



Aug, 3, 1954 Filed Au 31, 1950 aML TONE BUS V TONE um. [HOLDEN- ERMORTON ATTORNEY Aug. 3, 1954 w. H. T. HOLDEN ET AL FAULT SIGNALING SYSTEM FOR COUNTING CHAIN Filed Aug. 31. 1950 2 Sheets-Sheet 2 mwmwwfifi .l 06w N M MW M v .2 Z... .2. LT On aw 0R w H0 T J/ A w W F WE s 0 w m 8 NM w Patented Aug. 3, 1954 FAULT SIGNALING SYSTEM FOR COUNTING CHAIN William H. T. Holden, Woodside, and Edmund R.

Morton, Brooklyn, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application August 31, 1950, Serial No. 182,469

20 Claims.

This invention relates generally to signaling systems and more particularly to arrangements in such systems for detecting, counting, and registering signal impulses.

The main object of the present invention is the improvement of such detecting, counting and registering arrangements, particularly with reference to the rapidity of response to signal impulses and to the reliability of operation in response to such impulses.

In present-day signaling systems, such as may be useful with automatic telephone systems for instance, continuous improvement is being sought to increase the speed of response and to improve the reliability of circuits used for detecting, counting, and registering signals. in the telephone art in particular, continuous eiiort is expended towards devising and developing circuits which will respond more accurately and more reliably at a rapid rate to signals, such for instance as dial pulses or the like.

The present invention, while not necessarily restricted thereto as regards its utility or scope, finds ready application in automatic telephone systems where apparatus and circuits are necessary to accomplish these pulse detection, counting, and registering functions. An exemplary embodiment of the present invention is shown herein as capable of being incorporated in an automatic telephone system of the cross-bar type, such as that disclosed in Patent 2,585,904 to A. J. Busch of February 19, 1952. A skeletonized disclosure of the system shown in the Busch disclosure is set forth in Patent 2,616,974 to J. W. Dehn of November 4, 1952. The Dehn disclosure shown details of an originating register circuit of the cross-bar system, which circuit is comparable in context and function to the disclosure herein chosen as an exemplary embodiment of the present invention.

The function of an originating register, among others, in the cross-bar system disclosed by Busch and Dehn, is to receive, to detect, to count, and. to register dial pulse digits transmitted thereto under the control of a calling subscriber during the initiation by the latter of a request for a telephone connection.

An object of the present invention is the improvement of such circuitry as the above-mentioned originating register circuits in regard to the reliability of the functioning thereof and the rapidity of response thereby to signal impulses.

A specific object of the present invention is the provision of improved circuit means for enabling such circuits to be self-checking with re- 2 gard to the accuracy and reliability with which they respond to signal impulses.

The present invention, in one of its aspects, contemplates means for detecting impulses, a chain of electron discharge devices for counting these impulses under the control of the detecting means, and means for checking the response of the counting chain to said impulses. The counting chain is arranged to be stepped from device to device along the chain in response to impulses of a series such that at the end of such a series the last device activated represents the pulse count of the series. Means is provided for recycling the chain at the end of each series of impulses in preparation for counting the pulse content of a succeeding series. A check circuit is provided for detecting the failure of any device in the counting chain to be activated when it is supposed to be activated in response to an impulse. This circuit comprises a group of electron discharge devices which cooperate with each other, with the impulse detecting means, and with the counting chain to measure a time delay. Signal means is energized through the agency of said group of devices if the devices in the counting chain do not respond properly to impulses within the said delay time. This aspect of the invention is in the nature of an improvement over a similar check circuit arrangement disclosed and claimed in Patent 2,597,428 to A. E. Bachelet of May 20, 1952.

The check circuit comprises more particularly a pair of electron discharge devices which are energized alternately by successive pulses. After each pulse the condition of the said pair of devices is compared to the condition of the counting chain such that, if either the pair or the chain has not progressed properly in response to a pulse, the non-coincidence of the progressions will effect the energizing of a third device to indicate trouble. However, in the event that the progressions of the pair and the chain properly coincide, then the third device will not be fired. In the latter instance, a fourth device will be energized to indicate proper response of the pair and of the chain to each pulse.

Still more specifically, the check circuit comprises a first device energized by each pulse, a second device energized by the energization of said first device after a measured time delay to indicate trouble, a pair of cooperating devices designated for instance as odd and even devices which are energized alternately by successive odd and even pulses as their names imply, a third device energizable to indicate satisfactory operation, and voltage responsive means for testing the progression of said odd and even devices with the progression of the connecting chain after each pulse such that for coincidence of said progressions said means energizes said third device and for non-coincidence said means energizes said second device, the energization of said third device being effective to deenergize said first device thereby to immobilize said delay time measuring means.

The invention, outlined above, will be explained with the aid of the following detailed disclosure of the exemplary embodiment thereof, the drawings forming apart ofsuchxdisclosure being described generally as'iollows: I

Fig. 1 shows the pulse receiving, detecting, and counting circuits of a cross-bar; originating register circuit embodying the invention; and

Fig. 2 shows the registers and steering circuits of the originating register embodying the invention.

GENERAL DESCRIPTION The present invention is herein disclosed as embodied in circuits which. may be used in an automatic telephone system such as is disclosed in the above-mentioned Busch disclosure. Busch discloses in detail a cross-bar system wherein originating. register circuits areused for transmitting dial tone to calling subscribers, detecting and counting pulses of called digits, registeringthesecalled digits, and seizing an idle marker circuit for the-purpose of having such a marker complete the desired connection. Since the present disclosure of the invention. relates particularly to the pulsedetection, counting, checking and registering functions of an originating register, details other than ofsuch a circuit may be obtained from the Busch or Dehn disclosures. As may beobtained from the Busch or Dehn disclosure, the general sequence of events during the originating of a call by a subscriber is as follows:

(1) The calling subscriber lifts his receiver thereby seizing an idler marker circuit and auto- .matically informing I the seized marker that a dial tone connection is desired;

(2) ,The seized marker tests for and seizes an idle originating register circuit;

(3) The marker interconnects the calling line with the seized originating registercircuit over the cross-bar switch train and then the marker releases;

releases the originating register, completes the call, and thenreleases itself.

Since the present invention isdescribed herein as embodied only in circuits of an originating register, the subsequent detailed description will not cover items (1), (7) and (8) above. Such matters, however, are fully disclosed by Busch 4 and Dehn and are not necessary to the present description.

DETAILED DESCRIPTION Hereinafter whenever a part of the drawing is referred to by its reference character, such as l the ofi-normal-relay ON(1) the designation ON refers to the reference character which identi- ,.fies the part on the drawing, and the designation (1) refers to the figure of the drawing wherein that-q-part is", located. Thus the designation of relay ON(1) means the relay marked ON on Fig. 1, etc.

' Seizure of originating register Figs. 1 and .2, the off-normal relay ON(1) thereof isoperated by the marker. This relay ON(1) willremain operated as long as the register circuit is being used or until the register is released prematurely for one of a number or possible reasons.

Interconnection between calling subscriber and originating register After the seizure by a marker of an idle originating register circuit, the marker effects an interconnection over the cross-bar switch train betweenthe seized register and the calling line, thereby closing the ring and tip conductors ms and Nil or" the register over the calling line loop. The line relay L(l) is operated in a circuit extending from ground, over contact l of the dial tone relay DT(1), contact 2 of .the busy tone relay BT(1) leftwinding of relay L(l), tip conductor lllhqoverpthe switch train and the line loop, back over the ring conductor 109, right winding of relay L(l), to negative battery. (it is to be understood that whenever a voltage is indicated as negative or positive it is to be assumed that the opposite pole of thesource is grounded unless otherwisedesignated or men tioned.)

Relay L(l) upon operating on thev initial line loop closure performs three functions as disclosed:

(1) The slow-to-release relay S(l) operated in a circuit ironrnegative battery, through the winding of relay 8(1), through resistance I02, contacts! and 2 andarmatur of relay L(l), to positive battery; The relay S(l) is energized each. time that relay L(l) is operated (closed line loop) and is permitted to start releasing each time relay L(l) is released (open line loop periods representing. pulses of a.-.digit). Theslow-torelease characteristic of relay 8(1) assists in making sure thatrelay 8(1) does not release duringthe release. time of relay L(l) representing. pulses of a digit. There is another circuit phenomenon which further'assists relay 55(1) in remaining operated during the release time of relay L(l) Such phenomenon will be described presently.

(2) Condenser CH1) acquires a charge in a circuit extending. from positive battery (130 volts positive for-.instance),-over contact 2 of relay L(l), armature of relay L(l), resistance )3, to ground through condenserCl (1) Condenser Cl (1) acquires a positive charge upon its upper plate each time relay L(l) operates. This voltage will be approximately full battery potential (+130 volts) As will be described in'detail hereinafter, this charge on condenser Cl (1) is used asthe pulsing source for. controlling the counting chain. and control tubes whennrelay L(l)- rcleases in response to each open line loop pulse.

(3) Positive battery potential is applied over contacts 2 and I and armature of relay L(1), over conductor I04 to the circuits associated with the .gas tubes RA(1) and REG). Tubes RA(1) and RE(1) are normally extinguished and therefore their cathodes K are at negative battery potential (say minus 50 volts with respect to ground). Positive battery potential applied to conductor I04 starts the charging of condensers I05 and I06 in parallel circuits extending from conductor I04, through resistances I01 and I08, condensers I05 and I 08, resistances I09 and IIO, to negative battery. The rectifiers, such as rectia fier RE2( 1) in shunt of resistance I07, have little if any effect upon the charging time of the condensers because the rectifiers are so poled as to represent relatively high impedanoes when the voltage at their arrows is negative with respect to the other terminal. (These rectifier units will be encountered throughout the discussion and it is to be understood that when the arrow terminal is more positive than the other terminal, these units represent low impedances and will pass large currents readily; however, as has been men-' tioned, when the voltage polarity is reversed,- these units represent high impedances which however are finite-not open circuits.) The time constant of the charging circuit for condenser I06 is longer than that for condenser I05. Therefore, assuming that they are permitted to charge up at will, condenser I will acquire a sufi'iciently positive voltage on its left terminal, with respect to negative battery, to fire tube RA( 1) before tube RE(1) is fired by its condenser I00 This time difference is important with regard to subsequent discussion. The time constants are arranged such that tubes RAG) and RE(1) will both fire if relay LG) remains operated long enough to represent the pause between digits (interdigital time) and will thus probably fire upon the long pause between the first operation of relay L( 1) and the first pulse of the first digit.

When tube R.A(1) fires, by virtue of condenser I05 having acquired sufiicient voltage upon its left plate to break down the starter gap S-K,

tube RA(l) will pass a surge of current which will by-pass the anode resistance III through condenser I I2 which acts as a short-circuit under the transient condition. This current surge passing through the cathode resistance I 09 raises the potential at the cathode K of tube RAG) about 100 volts more positive; that is, to about plus 50 volts with respect to ground. This pulse is applied to conductor I I3 for purposes to be explained later. Very shortly however, the condenser I I2 becomes charged and loses its shunting effect thereby causing the anode potential of tube RAG) to drop. This drop of anode potentia'i in conjunction with the rise in cathode potential will extinguish tube RA( 1). Tube RAG) will not sustain another discharge until condenser H2 has dissipated its charge through resistance III and unless relay L(l) remains operated to recharge condenser I05. If relay L(l) remains operated for a sufficiently long time tube RAG) will refire at regular intervals thereby providing plus 50-volt pulses at its cathode K over conductor II 3. This initial application to conductor I I3 of pulses of about 100 volts magnitude positive with respect to negative 50 volts (that is, plus 50 volts) have no effect upon the other circuits as well be appreciated from subsequent discussion.

Similarly, when tube RE(1 fires, a plus 50- volt pulse is applied to conductor H4 from the cathode K of tube RE(1). Tube REG), like tube RA( 1), is self-extinguishing by virtue of the condenser II 5 shunting the anode resistance H6. The pulses applied to conductor II4 by tube RE( 1), as Will be explained hereinafater, will fire the start tube ST( 1) of the pulse counting chain but have no other eiiect at this time.

It will be observed that when relay L( 1) is released for any reason, the condensers I05 and I06 will lose their accumulated charges in parallel discharge circuits from negative battery, resistances I09 and H0, condensers I05 and I06, rectifiers RE2(1) and RE22(l), conductor I04, resistance I02, to negative battery through the winding of relay S 1). By virtue of the fact that the positive charges on condensers I05 and I06 find rectifiers RE2(1) and RE22( 1) low impedances for the discharges, the discharge times are always shorter than the charging times thus precluding the possibility of condensers I05 and I 06 integrating short pulses. That is, condensers I05 and I06 will always start timin from the same reference level of time and charge. Furthermore, these discharge currents will assist relay S(1) in remaining operated during the release of relay L(l) representingopen line loop pulsing periods.

Upon the operation of relay 8(1), above described, a circuit is completed for operating relay ON! (1) from ground, over the contact of relay 8(1), the contact of relay ON 1), to negative battery through the winding relay ONI(1). This ground extends to the sleeve of the switch connection over the dotted path I I I to hold the connection. Relay ON! (1), upon operating, applies positive battery (say 130 volts) over its contact to conductor 204 which supplies plate voltage to the tubes as well be described.

When relay ON I (1) operates, it fires the gas tube GL(1) in an obvious circuit. The tube GL(l) is continuously energized as long as relay ON 5 (1) is operated for the purpose of providing continuous light for keepin the rest of the gas tubes in the circuits energized so they will fire promptly and reliably. This, as will be obvious, is a well known keep alive means used extensively in gas tube circuits.

Upon the operation of relay .ONI(1), positive anode voltage is supplied to the main anode of the start tube STU) of the counting chain (tube ST( 1) through tube 0(1) of Fig. 1) over conductor 204, through the retard coil L2(I), and over conductor IIB. Tube ST(1) is normally extinguished thereby setting its cathode at minus 50 volts potential. When tube REG) applies the first -volt pulse (plus 50 volts) to conductor H4, this pulse is applied to the starter electrode of tube ST(1) from conductor I I4 over contact 4 of relay BT( 1) to tube ST( 1). This pulse of plus 50 volts raises the starter electrode of tube ST(1) some 100 volts positive with respect to the cathode and thereby fires tube STU). A surge of current passes to negative battery, through condenser H9 (in shunt of the cathode resistance I20), across the main gap of tube ST(1), over conductor II8, through the retard coil L2(1) from positive battery on conductor 204. The presence of condenser I I9 in shunt of resistance I 20 comprises eiiectively a short-circuit across resistance I20 during the surge transient. This insures that the cathode of tube ST(1) will remain at a negative 50-volt potential for a delay time determined by the time required to charge up condenser H0. This delay time is used throughout the counting chain, as

accesses .:Will be obviousfrom ansinspe'ction of the repeti- :.tive:nature of..-the cathode circuits; for .afpur- -.-pose. to. be; mentioned =later.. Eventually ;,con-

-denseril9-will-become charged to the steady state. cathode potential which will be approxi- -mate1y plus, 50 volts. cient to fire the gas diode DSTU) -connected This potential is .in'sufiibetween the cathode of tube. STU) and the plained, is attempting to .rise tov about plus 50 :'volts. If the condenser H9 wereanot -present, .condenser1i3l would delay. the rise of the plus 50 volt potential at the left electrode ofthe diode -DSTU) a. length of time, necessary to charge mcondenser. It'iv to this newly applied potential. Thus the delay caused by the charging of con- :denser I3! could be used for the same purpose as condenser H9 as far as-preventing the instant firing or diodeDSTU) is concerned. The circuit, as shown, is arranged such that the time "element represented by the, combination of condenser IE9 and resistance I20 is of the longer and-controllingduration, although it should be .remembered that condenser I31 does represent a time delay in the application or the plus 50 volt potential to the left electrode of tube DSTU).

i When relay ONI (l) operated, positive voltage wasapplied over the contact thereof, over conductor M4; through rectifier RTLU) and resistance I2 5, to -the starter electrode of the even -tub-e EU). Since the cathode of tube EU) is at minus 50 volts tube EU) will fire thereupon raising its cathode to about plus 50 volts. This 100 volt pulse iromthe cathode of tube EU) is useful as explained later in connection with .the check circuits. .starter electrode circuit of tube EU) is also con- It is to be noted that the nected toithe cathode of the start tube STU) by means of a rectifier unit RSTU) so poled that when tube STU) is fired the 100 volt positive pulsafrom thecathode of tube STU) will refire tube EU). It will be obvious that any further pulses from tube REU) over conductor Il l, asmsuming that relay LU) is still initially operated, will have no further effect upon tubes STU) and When relay ONI U): operated, positive .battery .was applied over conductor 2%, through the. retardcoil LIU), to'the :main anode of the, gas tube ONZU). This positive potential is also ap- .:-p.lie d. to the starter electrode of. tube ONZU) fromconductorlii through resistance I2I, con- ;,denser I?.2, ,and resistance 443,

.2JON2U). Before tube ONZU) fires its cathode, and thus conductor 2t2'is at approximately minus 1 50 voltsand the dial tone relay DTU) is released LadllQ-tO the fact that no current is flowing in the cathode resistance I23. When tubeON2U) fires,

-its cathode remains temporarily at about negative 50 volts; by virtue of the condenser 124 :shunting-thecathode resistance I23 as previously 'explained, and then rises to about plus 50'volts when condenser I24 becomes charged; The voltage drop across resistance I23 thereupon operates rela DTU). Relay DTU), upon operating applies dial tone over its contact 2, contact 2 of relay BTU), to the tip side of the line through the left winding ofthe line relayLU).

Upon hearingdial tone, the calling subscriber may "begin. to dial thewdigits of-the; called.'suba scriber s number, or other; called destination.

Thcpulse generation andcheck circuits A pulse is detected in the originating register by they release of the line relay LU); This repoperated .and the firin condensers I resents a -momentary open circuit inthe line which is, as is.wel1 known, the indication of a pulse.

When relay LU) releases, relay SU) remains and I06 of the tu es RAU) and REU) are discharged as 4 previously described.

When1re1ay LU) releases, the charge on con- .denser CI (1) is used to fire tube BKU) in a circult from condenser CIU), through resistance 103, contacts 3 and fiand armature of relay-LU) resistance I25, condenser I25 to negative battery .through resistance I21.

As soon as, condenser I26 charges up, tube BKU) will fire thereby raising its cathode some 100 volts to about +50 volts. The 100+volt positive pulse from the oathode of tubeBKU) is applied to three circuits:

to the cathode of tube SU) having noefiect at this time; to the starter electrode or" the trouble tube TRLU) through a delay network; and, to

the starter electrode of the pulse generation tube positive charge in PG 1) through a'delay network.

Condenser I30 in the starter-electrode circuit of the trouble tube TELU) begins to acquire a a circuit extending from the cathode resistance I21 oi-tube BKU); through resistances I28 and I29, condenser E36, to negative battery through the busy tone relay BTU). If condenser I39 is permitted to charge up for a sufficient length of time to fire tube TRLU). the firing of such tube will operate relay BTU).

--The-operation of relay BTU) will open at its contact the'firing circuit for the start tube STU) of the counting chain, will close over its contact I a circuit for sounding an alarm and for making the originating register busy so it may be tested, and over its'contact 3 closes a busy tone signal over the; tip IBI of the calling line through the left winding of the line relay LU) to inform the calling subscriber to disconnect and to try again. If the other-parts of the circuit function properly, 'certainmeans will cause the r promptly even in advance ured by condenser I3ii.

condenser I30 to discharge-before it can fire the troubletube TRLU). Similarly, in the event that certain parts of the circuit malfunction, other-means will insure that tube TRLU) fires of the time delay meas- These matters will be discussed asthey appear in the subsequent description.

Thepositive 100-volt pulse from the cathode of tube BKU) is applied to the starter electrode circuit; of the pulse generation tube PGU) through resistance itl; condenseri32, and cathode resistance I33 to negative'battery. After a time delay of some 7 to 8 milliseconds condenser I32'will have accumulated a'sufiicient charge to fire tube PGU); When tube PGU) fires it is self-extinguishing by virtue of the condenser I34 shunting the anode resistance I35, as was the case with thetubes' RAU) and REU), but will conduct for a period of time representing a finite pulse width. Tube PGU),,upon firing,,raises its cathode from 50 volts to about +50 volts and in so doing sends a 100-volt positive pulse out on the pulsing conductor l35-for advancing the pulse counting chain. Since the cathode of tube STU) is at +50 volts due to conduction-through tube STU), the -volt pulse on conductor I35 will fire the gas diode DST(I), interconnecting the cathode of tube ST(1) and the starter electrode circuit of tube I(1), through condenser I31. The resulting current surge through resistance I 38 creates a positive pulse sufiicient to fire tube H1). The relative magnitudes of resistances I33 and I36 are such that the voltage produced across resistance I38 when tube DST(l) fires, is due mostly to the pulse from condenser I31 and very little from the direct current connected to diode DST(1). Condenser I39 in the cathode circuit of tube I(1) keeps the cathode at --50 volts long enough to prevent the pulse on conductor I35 from also firing the gas diode DI (1). Eventually the cathode of tube I(1) will rise to +50 volts to condition the diode DI (1) to be fired on the next pulse on conductor I35.

When tube I(1) fires, the resulting current surge through the retard coil L2(1) drops the anode voltage of tube 8T(1) and, since con-v denser II9 retains the +50-volt potential on the cathode of tube ST(1) for a short period of time, tube ST(1) becomes extinguished by anode commutation. Thereafter the cathode of tube ST(1) reverts to minus 50-volt potential in order to prevent the refiring of diode DST(l) and tube I(1) unless tube 8T(1) is itself refired first. This counting chain interaction arrangement is disclosed and claimed in Patent 2,616,627 to W. H. T. Holden of November 4, 1952.

When tube PG(1) fires, the 100-volt positive pulse from the cathode thereof also is applied in parallel circuits through condensers I40 and I4I to the starter electrodes of respective odd and even tubes OD( 1) and E:(1). Since tube E;(1) is conducting, the positive pulse applied to the starter electrode thereof will have no effect. However, the positive pulse, when applied through condenser I40, will fire the odd tube OD(1). This conduction in tube OD(1) raises its cathode from --50 volts to about +50 volts. This positive pulse of 100 volts, when applied through the commutating condenser I42 to the cathode of the even tube E(1), extinguishes tube E(1) by cathode commutation.

The cathode of the odd tube O-D( 1) is connected through resistance I43 to the arrow terminal of rectifier RE8(1). The arrow side of rectifier RE8(1) is also connected through resistance I41 to the right terminal of a load resistance I 46 which is common to the cathodes of all of the odd counting tubes I(1), 3(1), (1), 1(1) and 9(1). Whenever an odd counting tube is conducting, such as tube I(1) responsive to the first pulse, the rectifier RI (1) connecting the cathode thereof to the common resistance I41 drives the right-hand terminal of such resistance I4! to a potential substantially that of the conducting cathode; that is, about +50 volts. If the odd tube OD( 1) is conducting, its cathode will be at approximately +50 volts also. The resistances I43 and I41 are so arranged that the junction therebetween will assume a potential which is the average of the two potentials derived from the odd tube OD(1) and from the odd counting tubes I(1), 3(1), 5(1), 1(1) and 9(1). Thus, if the odd tube OD(1) is conducting and if one of the odd counting tubes is also conducting, then the arrow terminal of rectifier REBQ) will be at +50 volts. Similarly, if the odd tube 013(1) is extinguished and all of the odd counting tubes are also extinguished, then the arrow terminal of rectifier RE8(1) will be at 50 volts. Furthermore, if the odd tube OD(1) is conducting or extinguished at the same time as the opposite the arrow terminal of rectifier REBG) will be at substantially ground potential (the average of -50 volts and +50 volts).

Without undue repetition it will be observed that the cathode of the even tube E(1) and the cathodes of the even counting tubes 2(1), 4(1), 6(1), 8(1) and II( 1) combine to set the potential on the arrow side of the rectifier REIQ) according to the average of the potentials supplied to the rectifier RE'I(1) through resistances I44 and I48, which are fed respectively from the cathode of the even tube 13(1) and from the load resistance I45 common to the cathode circuits of all even counting tubes.

Due to the arrangement of rectifiers RE'I(1) and RE8( 1), the right side of resistance I49 will assume a potential which is the more positive of the two potentials on the respective arrow sides of the rectifiers. That is, if the conduction through tube 013(1) coincides with the conduction through an odd counting tube or if the conduction through tube E(1) coincides with the conduction through an even counting tube, then the most positive potential of the arrow sides of said rectifiers will be +50 volts which is applied through resistance I49 to fire tube 8(1). If, however, neither of the above two coincidences occurs, then the most positive potential which can exist at the arrow sides of rectifiers RE'I(1) and RE8(1) will be substantially ground potential, which will be insufficiently positive with respect to the -50 volts on the cathode of tube 8(1) to fire said tube.

It will be apparent at thi point that the firing of tube 8(1) indicates a satisfactory check that the firing of an odd or even tube OD( 1) or E(1) from the pulse generation tube PG( 1) coincides correctly with the firing respectively of an odd or an even counting tube in the counting chain 1(1) to 0(1). In the instant case, as will be recalled, tubes OD( 1) and I( 1) are conducting. This coincidence drives the starter electrode of tube 8(1) about volts positive thereby firing tube 8(1). When tube 8(1) fires, tube BK(1) is extinguished by the positive pulse from the cathode of tube 8(1) through the agency of the commutating condenser I50 interconnecting the cathodes of tubes 8(1) and BK(1). When tube BKQ) is extinguished, its cathode returns to 50 volts (negative battery potential) as soon as condenser I50 discharges, thereby permitting condenser I30 in the starter electrode circuit of the trouble tube TRL( 1) to discharge quickly through the recti- 1 fier REI(1) which shunts resistance I28 for the purpose of discharge of condenser I 30. Thus when tube 8(1) fires, indicating a satisfactory check of the advance of the counting chain, the time delay measuring circuit for firing the trouble tube TRL(1) is immobilized, thereby preventing a trouble alarm.

On the other hand, if the counting tube I 1) or the odd tube OD(1) had not fired properly, assuming that both would not become inoperative simultaneously, then other means comes into play to fire the trouble tube TRL(1) instead of the check tube 8(1). Tube TRL(1) is energizable through two rectifiers RE5( 1) and REM 1) in a manner similar to the control of tube 8(1) by rectifiers IRE-1(1) and REM 1) However, the control of tube TRL(1) is difierent in that tube TRL(1) will be fired through the agency of its rectifier network only when a non-coincidence occurs. That is, byinspection, having previous discussion in mind, it will be observed that the arrow side of rectifier REEKl) is set to a potentialiwhich is. the average potential existing at the. cathodevof the even tube-E(1) and at the cathodeof any one or.

the odd counting tubes; Whereas, the arrow side of rectifier REGQ) is set to a potential which is the. average potential existing at the cathode of theodd tube OD(1) and at the cathode ofany one of the even counting tubes Furthermore the.

starter electrode of tube TRLCL) is energized-by themore positive of these two averages. :If the firing of the odd tube-OD(1) coincides with-the firing. "of uneven counting tube, then rectifieriiw REE (=1) will deliverabout a +50-voit pulse to tube TRL(1=) to fire samezand if the firing of the even:

tube 13(1) coincides with the firing-cf any odd counting tubegthen rectifier R135 (.1) willdeliver about a +50-volt pulse to tubeTELQ) .to fire same. Any other condition will never raise the potential of thestarter electrode of tube TRL(1) higher (more positive) than approximately ground potential which, of courseg-will not firetube TRL(1).

Assuming that tube 8(1) is fired accordingto previous description 'to indicate a satisfactory check of the advance of the countingzchain, relay :1.

ing circuits associated with tubes RACl) .and:

RE(1) are again energized .for timingan inter-v digital pause.

Counting initial digit of one pulse' Aninitialdigit of one pulse, unless followed directly by a second digit of onepulsexas Willbe explained, is assumed not .to be alegitiniate nal, because ofthe frequency; with which :such

erroneous-indication may be effected by acci-.. dental manipulation of the. subscriberis dial, by

spurious electrical impulses, etc. .Such an initial: digitis absorbed on the basis of the above assumption; but, as willbe explainedgit is not" dis-m carded in view or" the fact that asecond digit of onepulseis presumedto. indicate. a legitimate 11 prefix for a special code, such-as. a service code of 11X, where X may be any digitfromtzto 9.

In discussing the acticn-of-the pulse. counting chain, the special 11X circuits," and the steering"v and registering circuits it willbe assumed-that.

thepulse generation and check-circuits operate :1

normally so as to indicate: the proper advance .of"

the. counting chain. Previous discussion is ade-x quatefor an explanatiorrof trouble"conditione The normal functioning of thetpulse detection and checking circuits, as will be apparentfrorn previous discussion,- efiects the.followingzconditions:

(1) Each'time that the: line-relay;L( 1-) releases: and reoperates to indicate'a pulse of a digita.

pulse of about 100 volt positive nature is applied to the pulsing conductor I35; and,"

(2) Each time that the linerelay 11(1) remains operated for a sufficient time-to represent an interdigital pause, tubes RAG) and-REG) fireiin.

the pulse on conductor M3 by a'timedperiod.

At the end of the first digit of one pulse, as

above discussed, tube 1 (1) will be conducting and tube'STfl) will be extinguished; Due. to the con duction through tube l (1) the upper terminals of thetwo gas diodes TDHifl) and-TDIHL) con-. nected to the cathode of tube-l(1) willbe setiat its plus :50 volts after a delay of tirneafterthe firing of tube -!(1)- necessary to chargecondensers C3(l') and1C4(l) to the newly applied potentiaL. The. lower terminalsof tubes .TDHl(1) and TDiHl) are ccnnected'over respective conductors 2H] and 2H in parallel to ground through resistances-268 and 209- and through respective condensers 206 and 201 to the upper terminalsof respective gas diodes TDAEKZ) and TDAHQ) of Fig. 2 associated with the A digit registertubes AWZ) to AC7).

The diodes TDAM'Z), TDAI.(2),. TDAZ(2),

TDAMJZ), and TDAI(2) are all controlled,=.as

regards the potential on their upper terminals,

from the cathode of the A digit steering :tube A(2). With the tube -A(2) non-conducting;:.its

cathode, and thus the upper terminal of the A register diodes, is at negative battery potential (minus 50 volts)from conductor 263." timethat a register tube, such as tube AM'Z) or A! (2) canbe fired to register a-digit isiwhen. the two 'diodes,.such as 'IDi6(1) and .TDi.l.(1), assoe'.

ciatedwith'a countingtube, suchas tube.l(1),

canafirei in cascade. with two corresponding tubes, suchq'as "diodes JTDAMZ) "and .TDAH'2) or etc., or TDGEHZ) and:

TDBMZ) and-:iTDB-l (2)3, TDGl (2) ,1 associatedtwithx a particular group .of

register'tubes. This. conditionv exists onlyiwhen the associated.steeringtube, such as .tubetA(2') is conducting and when: the associated rcounting tube, such as tube [(1) is conductingrJWhena countingiztube; such as tube.l.1(1) is conducting, thelOOvolt positive pulse from vithe tube RAH) OVGIYCOIIdllCtDlSTl'. L3 will fireiboth associated diodes,

such as'diodesTDlflrl). andTDll (1) because the 100..volt"pulse will drive theupper, terminals of the diodes1to about plus 150volts;vvhich. is sulficientzto' fire: them: since..their 'lowerrterminals are'returned toground. over'conductors 219 and 2! l andzthrough resistances 2B8. andJZfiS. The resulting pulse of. about plus 1-00. volts developed across these resistances to fire all register.tubezdiodeasuch asv TDAM2) and-:TDAI(2),".TDBM2) 'and.;.TDB.!(2),; etc., TDGMZ) and TDGI (2), volts is insufficient. to fire ever, unless they have.

these diodes. howthe associated steeringtubes are non-conducting.

.Thusthe pulse, generated by tubeRA(1) is not effectiveto register the first digit'of one pulse. As soonas the pulse from tube R'A(l) ceases; the diodes and such as TDliHl), TDI|(1), which may have fired are extinguished.

A short interval after the pulse on conductor H3Lfrom tube RAG), tube REG) generates a LOO-volt positive pulse on conductor H4, as has been .desc'ribed.- The gas diode PPD(1) in the starter electrode circuit of tube 'PP(1) is controlled. from three quarters. The pulsing conductor H4 from tube REG) is connected thereto through condenser 15! Also, the cathode of tube i(1) is connected thereto through the resistance i52'and rectifier .RE3(1). Furthermore, the cathode'of tube ON2(1) is connectedthereto through the resistance I53 and rectifier RE4(1). The right terminal of the gas diode PPD(1) is at ground potential through resistance I54 and therefore it will require apulse of at least 100 positive volts to fire the diode: PPD(1). The

The only" associated therewith.

been enabled by having their upperterminals raisedzto plus50 volts from common connection between rectifiers RE3(1) and RE4(1) will, due to the polarity of such rectifiers, assume the more negative potential of the respective arrow terminals. At the end of the first digit of one pulse both cathodes of tubes IQ) and ON2(1) are at plus 50 volts and thus the left terminal of the diode PPD(1) will be at plus 50 volts. The 100 volt positive pulse on conductor I I4 from tube RE( 1) will thus fire the gas diode PPD(1) and the latter, through the agency of the current surge in resistance I54, will fire the tube PP(1). The condenser I 55 shunting the cathode resistance I56 of tube PP(1) holds the cathode of tube PP(1) at minus 50 volts long enough to prevent the firing of tube I I (1) on the first pulse from tube REG). Eventually condenser I55 becomes charged and the cathode of tube PP(1) rises to about plus 50 volts to condition the diode DII(1) so that it will fire tube II(1) on a second digit of one pulse.

In addition, when tube RE(1) generates the interdigital pulse on conductor N4, the start tube STU) is refired over the contact 4 of relay BT(1). The resulting current surge through tube ST(1), as has been explained, extinguishes the tube I( 1) by anode commutation and the circuits are ready to receive the next digit.

It will be observed that none of the steering tubes, such as tubes A(2) to H(2), have been operated in response to the first digit of one pulse and. that, although this first pulse has been absorbed by the firing of tube PP(1), the first pulse has not been discarded.

Furthermore, it will be seen that the abovedescribed means for transferring the pulse count from the counting tubes of Fig. 1 to the register tubes'of Fig. 2 involves two gas diodes for each counting tube, such as diodes TDIO(1) and TDII(1) for counting tube I(l). These diodes, under proper conditions as have also been indicated, will fire two-outof-five register tubes, such as tubes A!i(2) and AI (2). This two-out-of-five code is well known and is arranged as follows:

produces a 100 volt positive pulse on conductor H3. This pulse will, as before, fire the gas diodes TD! 0(1) and TDI I (1) associated with the cathode of counting tube H1). However, since the steering tube A(2) of Fig. 2 has not been energized, the digit one, represented by the firing of the diodes TD!0(1) and TDI I (1), will not be registered in the A digit register tubes A0(2) and Al (2).

Subsequent to the firing of tube RAG), tube REG) fires to produce on conductor 4 a 100 volt positive pulse. By virtue of the fact that tube PP 1) is conducting, as has been explained, the cathode thereof, and thus the left terminal of the gas diode DI I (1) is raised to plus volts. The pulse on conductor I I4 will fire the diode DI I (1) through condenser I51 thereby firing the tube II(1). The cathode of tube (1) will be raised to plus 50 volts thereby raising the potential of conductor 2! from minus 50 volts to plus 50 volts. The energization of conductor ZBI is an indication that an 11 prefix has been detected and registered in the counting circuit. This indication is used in a manner presently to be described. When tube Il(1) is fired it extinguishes tube PP(1) by cathode commutation through condenser I58.

Further detection of digits of one pulse each, whether intentional or not, Will have the efiect merely of alternating the conduction in tubes PP(1) and HG). A timing circuit (not shown) may be provided which, under this condition, will eventually call in a marker circuit for the purpose of switching the calling line to a permanent signal tone trunk to call in an operator for trouble analysis. Examples of such circuits are fully described in Busch and Dehn disclosures above-identified. Such circuit may also be used to indicate a total failure of the calling line to dial any digits at all or to indicate the receipt by the originating register of only one pulse followed by a continuous operation of the line relay L(l). Other trouble conditions may be met by Digit Counting Chain Diodes Fired Register Tube Diodes Fired 'Reglster Tubes Fired TDAO(2)-TDA1 (2) 'IDAO(2)TDA2(2) TDAl (2)-TDA2 (2) 2( 7(2) '1D104 (1)-TD 107(1) TDA4(2)-TDA7(2) Counting a second digit of one pulse tubes O-N2( 1) and H1) are both conducting, the

left terminal of the gas diode, PPD(1) is raised to plus 50 volts. Since tube H1) is energized, the upper terminals of the gas diodes TDIMI) and TDI I (1) are again raised to plus 50 volts.

When relay L(l) reoperates at the end of the first pulse and remains operated to indicate the time delay between digits, tube RA(1) fires to other known circuits but, since the present invention is not particularly concerned with such expedients, none of these circuit means is shown or described.

Counting and registering the X digit of an 11X code It will be assumed that, after the dialing of tWo digits of one pulse each, the calling subscriber dials a digit greater than one pulse, such as three pulses, to'indicate a special 11X code.

Upon the first release of relay L(l), the resulting pulse on conductor S35 fires tube I(1), thereby extinguishing tube ST(1). The second release of relay L(l) occurs before tubes RA( 1) and REG) can fire and thus the second pulse on conductor I35 fires tube 2(1), thereby extinguishing tube H1). When tube 2(1) fires, its cathode is raised to plus 50 volts thereby producing a volt positive pulse to the starter elecaces-pea:

troder-of tuberAZfl): overiconductortfim whnli tubes. A2 (11) firesltzit eXtinguishes -itseli? by virtue. L of .the:.:anode. circuitzarrangement':toi condenser appliedathroughztcondenser .I (52 i to conductor 2 ii 2. 1

Since conductor 292 was originally at plusbi) voltsrfdues to conduction .;.through tube. N2 (1),

thei'conductor 2 32! '-.is now; momentarily provided.

Withxa pulse-.extendingrtto about "plus .150' :volts...

This pulse-rwilrfire.the; gas diode-DA.(2) to in turnifire'. the steer-ingLtube A(2 Condenser *2 I 5 in the cathode circuit-of tube M2) .will hold the cathode at :minusbi) voltstfor a .shortilength of timefand: then: willpermit" the cathode to assume a potential for aboutrplusEO ivolts'. This plus 50 volt @otentialwill enable the gas diode DB (2) to be fired'by the next pulse on conductortOS from conductor. H4 at thet'end of. thenextdigit. This plus-50 voltpotentialrrom: the cathode of tube A(2)1.a1so raises.theipotentialz'of the upper ter-i suc'lrthatithis three pulse digit will be registered in the A digit register tubes.

When :atub'e .A(2) fires, 'the .surge' of current through retard coil LI ('1) over conductor 208,1: extinguishesitub'e ONE (1). Tube ON2(1),'

upon ceasing to conduct, :releases the dial tone rela'y JET-('1).

Thus-nit will be 'observedydigits may be re isteredain thelregistersof Fig; 2 onlyafteria digit of'more-ithan'one pulse is counted by the counting'zcircuits iof Fig; 1. J

Relaylz-(I) .willireoperateand release again.-

before" lMbES/RAQ) and REG) can fire thus producingza third pulse on conductor ...I '55. I This pulserwill :fire itube 3(1) which in turn will 'ex-' tinguisht tube 2 (1) At this'ijuncture; tubes 'A(2) 3(1), Land: I I.( 1) P willnbe opera-ted; when relay 11(1). releasesat the end of the three pulse digit, tube RA(1 fires to produce a 100 volt positive pulse on con-: This pulse will fire gas diodes ductor H3. TD3I (1) and TD32(1) associated with the conducting tube 3(1).

The firing of these diodes.

will create positive pulses across the resistances- 209 and 215 respectively of Fig. 2 due to p.as' sage of current therethrough from the diodes Since the upper.

over conductors 2H and ZIZ.

terminals of the gas diodes TDAI(2) '"and TDA2(2) are at plus volts due to conduction in tube M2), the positive pulses across resistances 2G3 and'zle-willfire these diodesywhich,"

in turn,"willcausesurges of current in resistancesZI'I 'and "2 I8 to fire tubes Al (2) and 112(2). The tubes AI (2) and A2(2) will remain conducting to indicate the registration, on atWo-out-offive basis, of the digit. 3.-

Subsequent to the pulse from tube RAG), tube REM) fires to produce a 100 volt positive pulse on conductor .I I4. tub'eSTfl), thereby extinguishing tube 3(1) to recycle-zthe.icounting chain. .This pulse will also be appliedro'ver conductor 2% to fire the diode 1313(2) through'condenser 2I9. The firing or diodeuDB 2 causes the 13 digit steering tube 13(2) to conduct: and to extinguish tube A(2) by anode This pulse will refire commutationxthrough the. agency of retard coil LI(1);-.. The condenser 223 "across the cathode resistance. 225 of tube 13(2) holds the cathode at minus 50 :volts long enough to prevent the firing fof the diode DC-(2) by the *presentrpulse:

on conductor 11 2.0 5: i Eventually;iwhenrthetzcon denser 223 becomes charged -the cathode. ottube B 2:.) 'f will-"rise to. plus:.50 VOltS.ff.L.l'ThlSFTlSS.10f potenti'al primes: the diQdesZTDBBCZ'); -.TDBI62)-, i

digitaregisteri so -that11two-outsof-fiiie' of these diodes-will be fired to register thenext digit. When tube A(2)f was extinguished, the'plus150 volt priming. potentialwas removed from the cor-2' responding: A digit register diodes. so that the A digit. register .cannotbe 'affectedsby subsequent i digits. Thisarrangement' of selectively firing. gas diodes in cascade-for the purpose-of causing. registrations is disclosedrand cl-aimed'in Patent 2,678,409 to W. H. T. Holden of. May. 11, 1954.: On 11X codes it is the practice for the originating-register to fcallzin a marker circuit as soon as the X digit is registered inthe A digit. regis ter. The indication that such: hastaken place is the firing of the 3 digit steering: tube-13(2).

It will be recailedtha-t theconduction by tube 3 I (1)- raised the potential of conductor ZEN-from minus 50 voltsto plus 50 volts by virtue'of the connection of the cathode of tllbB: I I (1) to conductor:2ill.- When tubeB(2) fires, its cathode raises the potential of conductor226 from1ninus. 50 volts to plus'50 volts; These-two conductors 20 l and 226- are connected to the top terminals of respective rectifiers RI H2) and .RI2 (2);; These rectifiers a re=arranged and poled such that their connected arrow terminals *will assume: a. potential which-is the more negative of the two potentials on conductors 2M and 22%.: 11": either or bothoi conductors 26i and-2-2t is at minus50 volts, thenthe arrow terminals of rectifiers: RE I (2) and 1812(2) will be at substantiallyminus 50 volts and tube HI (2) will not fire. However, if both of conductors 2M and'226 are-at plus 50 volts; asthey will be under thepresent conditions of an-llxcode (a codeof 113 in the example), then-thearrow terminals of rectifier BI I (2). and BI2(2);--will rise to about-plus 50 volts and .will therefore fire tubal-II (2) through the rectifier RI4(2).

When tube vHI(2) fires, it extinguishes tube 13(2) by anode commutation-and operates the mar-ken start- -relay -MST(2).- Relay-M5112), upon'operating, causes'the'seizurei of an idle marker. circuit for the purposes of completing the 'desired call, which, in the case of an 11X service code, may be to a suitable operator.---

Regular seven digit local call' For-calls which are directed to local subscribers, there will be no 11 prefix and the digits dialed may representthefamiliar.A, B, and Ooffice digits followed by'four station numericals. In this case the-first digit will be greater than one pulse-and thus-will be registered'in the A digit registerr- The'nextsix digits will be successively registeredfin' the B, C, D, E, F, and G registers. At the end of the registration of the G or seventh digit, tube H(2) will be fired thereby operating relay'MST(2)- to seize an idle marker circuit for the purpose of completing the desired connections." During this sequence of operation; the tube HI (2) will not be fired when the 13 digit steering tube B(2) conductsbecause conductor 20 I will be at minus 50 volts dueto the fact that tube I I (1') was not fired.

A zero operator call registertubeszAtQ) and A'HZ). These two tubes i? would raise the potential of conductors 228 and 229, connected to their respective cathodes, from minus 56 volts to plus 50 volts. As was the case with the 11X codes, making conductors 2M and 226 both plus 50 volts, these two conductors 228 and 229 will increase the potential of the arrow terminals of rectifiers 1%(2) and RHMZ) from minus 50 volts to plus 50 volts thereby to fire tube I-IHZ) and operate relay MST(2). This action seizes an idle marker after the first digit is registered for the purposes of switching the calling subscribers line circuit to an operator, as desired.

Marker operation When an idle marker (not shown) is seized due to the operation of relay MST(2), the register tubes of Fig. 2 are connected to the seized marker over cable 238 for the purpose of transferring the registered information to the marker. The tran fer is made by circuits in the marker which can detect which cathodes of which register tubes are at plus 50 volts. The marker is also supplied (by means not shown) with other information concerning the call, such as the location of the calling subscribers line circuit in the oifice plant, the class of service. to which the calling subscriber is entitled, the nature of the call (11X call, zero operator call, etc), etc. From this information the marker proceeds to supply the service requested.

While the invention has been disclosed herein by way of example as embodied in a circuit using cold cathode gas discharge tubes, it will be an obvious modification within the skill of the art to substitute hot cathode thyratrcns for the cold cathode tubes, in order for instance to embody added speed of operation in the circuits.

Furthermore, with regard to the voltage responsive gates, which in the exemplary embodiment comprise gas discharge cold cathode diodes, it will be an obvious modification to substitute for these diodes other known suitable gating means, such, for instance, as dry rectifiers or the like.

As far as the utility of the present invention is concerned, while it has been disclosed herein as embodied in a decimal or decade counter circuit arrangement, it will be apparent to those skilled in the art that the invention may be applied within its spirit and scope to other similar circuit arrangements, such as binary counters, digital computer circuits, etc.

It is to be understood that the above-described arrangements are merely illlustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. In a signaling system, a source of pulses, an electronic discharge tube counting chain, a pair of electron discharge tubes, control means for applying a train of pulses concurrently to said counting chain and to said pair of tubes, said counting chain responsive to said control means to alter the conducting condition of successive tubes of said chain in response to successive pulses of a train, said pair of tubes responsive to said control means to cause one of said pair to conduct and the other to become extinguished alternately in response to alternate pulses of a train, and means for detecting whether or not said counting chain and said pair of tubes respond concurrently to successive pulses of a train.

2. In a signaling system, a source of pulses, a

gas tube counting chain, a pair of gas tubes, control means for applying a train of pulses concurrently to said chain and to said pair, said chain responsive to said control means to cause conduction in successive tubes of said chain in response to successive pulses of a train, said pair responsive to said control means to cause conduction in alternate ones of said pair in response to alternate pulses of a train, and means for detecting whether or not said chain and said pair respond concurrently to successive pulses of a train.

3. In a signaling system, a source of pulses, a gas tube counting chain, a pair of tubes comprising an odd gas tube and an even gas tube, control means for applying a train of pulses to said chain, the first pulse of said train causing conduction in the first tube of said chain, commutating means interposed between successive tubes of said chain whereby successive tubes of said chain are rendered conducting in response to successive pulses, said control means arranged to apply said train of pulses concurrently to said pair of tubes, the first pulse of said train causing conduction in said odd tube, commutation means interposed between said pair of tubes whereby alternate ones of said pair of tubes are rendered conducting in response to alternate pulses, and means for detecting whether or not said counting chain and said pair of tubes respond concurrently to successive pulses of a train.

i. In a signaling system, a source of pulses, a gas tube counting chain, a pair of tubes com prising an odd gas tube and an even gas tube, control means for applying a train of pulses to said chain, the first pulse of said train causing conduction in the first tube of said chain, commutating means interposed between successive tubes of said chain whereby successive tubes of said chain are rendered conducting in response to successive pulses, said control means arranged to apply said train of pulses concurrently to said pair of tubes, the first pulse of said train causing conduction in said odd tube, commutation means interposed between said pair of tubes whereby alternate ones of said pair of tubes are rendered conducting in response to alternate pulses, means for detecting whether or not said counting chain and said pair of tubes respond concurrently to successive pulses of a train, means operated under the control of said detecting means to indicate concurrent response, and means operated under the control of said detecting means to indicate the failure of concurrent response.

5. In a signaling system, a source of pulses, a common pulsing conductor, a gas tube counting chain, a pair of cooperating gas tubes comprising an odd gas tube and an even gas tube, a control gas tube rendered conducting in response to each pulse, means for applying a pulse over said conductor to said counting chain in response to each conduction in said control tube, the first pulse causing conduction in the first tube of said chain, commutating means interposed between successive tubes of said chain whereby successive tubes are rendered conducting in response to successive pulses, means for applying a pulse over said conductor to said pair of tubes in response to each conduction in said control tube and independently of said counting chain, the first pulse causing conduction in said odd tube, commutating means interposed between said pair of tubes whereby alternate ones of said pair are rendered conducting in response to alternate pulses, means for detecting whether or not said counting chain and said pair of tubes respond concurrently and independently to successive pulses of a train, a check tube, and a trouble tube, said detecting means arranged. to cause conduction in said check tube to indicate concurrent respouse and to cause conduction in said trouble tube to indicate a failure of concurrent response, and circuit means controlled by said check tube for causing said control tube to be extinguished solely in response to conduction in said check tube.

6. The invention as claimed in claim wherein said detecting means comprises a voltage responsive means controlled jointly from said counting chain and from said pair of odd and even tubes.

'7. The invention as claimed in claim 6 wherein said voltage responsive means comprises a network of asymmetric impedance devices interconnecting said counting chain and said pair of odd and even tubes with said check tube and said trouble tube.

8. The invention as claimed in claim 7 wherein said asymmetric impedance devices comprise rectifiers.

Q. The invention as claimed in claim 8 wherein said rectifiers are so arranged in relation to each other and to the counting tubes, to the pair of odd and even tubes, to the check tube and to the trouble tube such that whenever an odd counting tube and the even tube of said pair are conducting concurrently or whenever an even counting tube and the odd tube of said pair are conducting concurrently said rectifiers will cause conduction in said trouble tube and such that whenever an odd counting tube and the odd tube of said pair are conducting concurrently or whenever an even counting tube and the even tube of said pair are conducting concurrently said rectifiers will cause conduction in said check tube.

10. The invention as claimed in claim 9 wherein said counting tubes, said pair or odd and even tubes, said check tube and said trouble tube are three-element gas tubes and wherein said rectifiers interconnect the cathodes of said counting tubes and of said pair of tubes with the starter electrodes of said check tube and of said trouble tube.

11. The invention as claimed in claim 10 wherein a first group of said rectifiers interconnects the cathodes of the even counting tubes and of the odd tube of said pair with the starter electrode of said trouble tube and a second group of rectifiers interconnects the cathodes of the odd counting tubes and of the even tube of said pair with the starter electrode of said trouble tube and a third group of rectifiers interconnects the cathodes of the even counting tubes and of the even tube of said pair with the starter electrode of said check tube and a fourth group of rectifiers interconnects the cathodes of the odd counting tubes and of the odd tube of said pair with the starter electrode of said check tube.

12. The invention as claimed in claim 11 wherein each group 01 rectifiers includes at least one rectifier exclusive thereto.

13. In a signaling system, a source of pulses, a common pulsing conductor, means for applying a train of pulses from said source over said conductor, step-by-step counting means responsive to a train of pulses on said conductor to be advanced thereby step by step, a dual condition means responsive concurrently with and independently of said counting means to a train of pulses on said conductor to assume alternate conditions in response to alternate pulses of a train, and means for detecting whether or not said counting means and said dual condition means respond concurrently and independently to a train of pulses on said conductor.

14. In a signaling system, a source of pulses, a common pulsing conductor, step-by-step counting means, control means for applying a train of pulses from said source over said conductor to said counting means whereby said counting means is advanced one step for each pulse of said train, a dual condition means, control means for applying a train of pulses from said source over said conductor to said dual condition means independently of said counting means whereby the condition of said dual condition means is altered for each successive pulse of said train concurrently with and independently of the action of said counting means, and means for detecting whether or not said counting means and said dual condition means respond concurrently and independently to successive pulses of a train.

15. In a signaling system, a source of pulses, a common pulsing conductor, step -by-step counting means, a dual condition means, control means for applying a train of pulses from said source over said conductor concurrently and independently to said counting means and to said dual condition means, said counting means responsive to said control means to advance one step for each pulse of said train, said dual condition means responsive to said control means independently of the action of said counting means to assume one condition for each even puls of said train and the other condition for each odd pulse of said train, and means for detecting whether or not said counting means and said dual condition means respond concurrently and independently to successive pulses of said train.

16. In a signaling system, a source of pulses, a common pulsing conductor, an electronic discharge tube counting chain, a pair or" electron discharge tubes, control means for applying a train of pulses from said source over said conductor concurrently and independently to said counting chain and to said pair of tubes, said count ing chain responsive to said control means to alter the conducting condition of successive tubes of said chain in response to successive pulses of a train, said pair of tubes responsive to said control means independently or said counting chain to cause one of said pair to conduct and the other to become extinguished alternately in response to alternate pulses of a train, and means for detecting whether or not said counting chain and said pair of tubes respond concurrently and independently to successive pulses of a train.

17. In a signaling system, a source of pulses, a common pulsing conductor, a gas tub-e counting chain, a pair of gas tubes, control means for applying a train of pulses from said source over said conductor concurrently and independently to said chain and to said pair, said chain responsive to said control means to cause conduction in successive tubes of said chain in response to successive pulses of a train, said pair responsive to said control means independently of said counting chain to cause conduction in alternate ones of said pair in response to alternate pulses of a train, and means for detecting Whether or not said chain and said pair respond concurrently and independently to successive pulses of a train.

18. In a signaling system, a source of pulses,

a common pulsing conductor, a gas tube counting chain, a pair of tubes comprising an odd gas tube and an even gas tube, control means for applying a train of pulses from said source over said conductor to said chain, the first pulse of said train causing conduction in the first tube of said chain, commutating means interposed between successive tubes of said chain whereby successive tubes of said chain are rendered conducting in response to successive pulses, said control means arranged to apply saidtrain of pulses from said source over said conductor concurrently to said pair of tubes independently of said counting chain, the first pulse of said train causing conduction in said odd tube, commutating means interposed between said pair of tubes whereby alternate ones of said pair of tubes are rendered conducting in response to alternate pulses, and means for detecting whether or not said counting chain and said pair of tubes respond concurrently and independently to successive pulses of a train.

19. In a signaling system, a source of pulses, a common pulsing conductor, a gas tube counting chain, a pair of tubes comprising an odd gas tube and an even gas tube, control means for applying a train of pulses from said source over said conductor to said chain, the first pulse of said train causing conduction in the first tube of said chain, commutating means interposed between successive tubes of said chain whereby successive tube of said chain are rendered conducting in response to successive pulses, said control means arranged to apply said train of pulses from said source over said conductor concurrently to said pair of tubes independently of said counting chain, the first pulse of said train causing conduction in said odd tube, commutating means interposed between said pair of tubes whereby alternate ones of said pair of tubes are rendered conducting in response to alternate pulses, means for detecting whether or not said counting chain and said pair of tubes respond concurrently and independently to successive pulses of a train,

means operated under the control of said detecting means to indicate concurrent response, and means operated under the control of said detecting means to indicate the failure of concurrent response.

20. In a signaling system, a source of pulses, a gas tube counting chain, a pair of cooperating gas tubes comprising an odd gas tube and an even gas tube, a control gas tube rendered conducting in response to each pulse, means for applying a pulse to said counting chain in response to each conduction in said control tube, the first pulse causing conduction in the first tube of said chain, commutating means interposed between successive tubes of said chain whereby successive tubes are rendered conducting in response to successive pulses, means for applying a pulse to said pair of tubes in response to each conduction in said control tube, the first pulse causing conduction in said odd tube, commutating means interposed between said pair of tubes whereby alternate ones of said pair are rendered conducting in response to alternate pulses, means for detecting whether or not said counting chain and said pair of tubes respond concurrently to successive pulses of a train, a check tube, and a trouble tube, said detecting means arranged to cause conduction in said check tube to indicate concurrent response and to cause conduction in said trouble tube to indicate a failure of concurrent response, and circuit means controlled by said check tube for causing said control tube to be extinguished solely in response to conduction in said check tube.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,726,009 White Aug. 27, 1929 2,088,793 Judge Aug. 3, 1937 2,373,134 Massonneau Apr. 10, 1945 2,589,465 Weiner Mar. 18, 1952 2,597,428 Bachelet May 20, 1952 

